The invention relates to marine drive cathodic protection systems.
Marine drive cathodic protection systems are known in the prior art. It is known that a marine drive can be cathodically protected from corrosion by supplying electrical current from a power source to an anode for flow through water as anodic ionic current to a cathode provided by a submerged metal section of the marine drive. A current controller operates to maintain the surface of the marine drive at a desired potential by supplying current to the anode in response to electrical reference potential sensed by a reference electrode, whereby to impress voltage across the load presented by the junction of the surface of the marine drive and the water in which the marine drive is submerged.
It is known to provide shielding for the reference electrode from the anodic ionic current, e.g. by providing a shield blocking or diverting electric field flux lines, or by providing spatial distance between the anode and the reference electrode diminishing electric field flux line intensity. It is also known to provide a variable bias signal to a power transistor controlling the amount of anode current, which bias signal increases as the anode current increases. The increasing bias signal compensates for the voltage drop through the water between the reference electrode and the noted load, which increases with anode current and serves to hold the potential at the surface of the protected marine drive essentially constant, regardless of the anode current.
The present disclosure arose during continuing development efforts in the above technology. In one aspect, the disclosure eliminates the need for shielding the reference electrode from anodic ionic current, whether by a shield blocking or diverting electrical field flux lines, or by a shield provided by spatial distance between the anode and the reference electrode diminishing electric field flux line intensity. In another aspect, the disclosure eliminates the sensing of anodic ionic current induced voltage in the reference potential sensed by the reference electrode and the need to compensate same.